Two-pion production in proton-proton collisions with a polarized beam (original) (raw)
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The European Physical Journal A, 2004
The detailed investigation of the reaction pp → ppπ 0 has been carried out at two incident proton momenta. Momentum, angular and effective-mass distributions were analyzed in the framework of the onepion exchange model. Taking into account only the P33-wave in the pole diagrams allows one to obtain a good agreement with experimental data on differential distributions. At the same time the predictions for total cross-sections are much lower than the experimental data.
The European Physical Journal A, 2010
A detailed investigation of the reaction np → ppπ − has been carried out using the data obtained with the continuous neutron beam produced by charge exchange scattering of protons off a deuterium target. A partial wave event-by-event based maximum likelihood analysis was applied to determine contributions of different partial waves to the pion production process. The combined analysis of the np → ppπ − and pp → ppπ 0 data measured in the same energy region allows us to determine the contribution of isoscalar partial waves (I=0) in the momentum range from 1.1 up to 1.8 GeV/c. The decay of isoscalar partial waves into (1 S0)ppπ channel provides a good tool for a determination of the pp S-wave scalar scattering length in the final state which was found to be app = −7.5 ± 0.3 fm.
Positive Pion Production in Proton-Nucleus Collision
Progress of Theoretical Physics, 1977
Positive pion production process on 12 C by 185 MeV proton is studied within the framework of DWBA by adopting the Kisslinger-type optical potential for the final state interaction. The qualitative features of this reaction are explained if the off-shell part of the optical potential is modified by introducing the vertex function. This modification scarcely affects elastic pion-nucleus scattering. § 1. Introduction Pion production process (p, n+) on nuclei is one of the interesting phenomena m pion-nucleus interactions.v~sl As a neutron is transferred into the target nucleus, this reaction is analogous to the ordinary nuclear reactions, such as (d, p) and (n, r). Since the measurements of the cross sections of 12 C (p, n+) 13 C by the U ppsala group by the use of the 185 MeV proton beams,7)~lol this reaction has been paid much attention theoretically.11)~,sl Most of the theoretical work was based upon the DWBA theory by adopting the Kisslinger-type optical potential for describing the emitted pion! 1 l, 25 l and the conventional static pion-nucleon interaction for the vertex of pion production. The calculated values of the cross section were shown to be larger than the experimental values by one or two orders of magnitude.m. 18 l In this connection, Miller found the parameter set of the Kisslinger-type optical potential which explains elastic scattering and the (P, n+) reaction on 12 C. 19 l His parameters are, however, quite different from those commonly used in elastic scattering on 12 C." 6 l~zsl Recently Miller and Phatak 20 l have calculated the 12 C (P, ni) 13 C reaction cross section, using the separable pion-nucleon potential proposed by Landau et al." 9 l~sJJ Although the results are in agreement with the experimental data, the range parameters adopted for the nuclear form factor are somewhat too large. Besides, the vertex of pion emission was also investigated by Lee and Pittel, 22 l and by Noble. 23 l From the kinematical consideration the above complicated situations can be ascribed to the off-shell behavior of pion-nucleon interaction, to which elastic pionnucleus scattering is rather insensitive: If we switch off the initial and final state interactions in the above reaction, the momentum of the transferred neutron is 460~660 MeV/ c, \vhich is far above the Fermi momentum. Therefore, the cross section for this reaction is expected to be very small. However, if we take into
Large-angle production of charged pions with 3–12.9 GeV/c incident protons on nuclear targets
Physical Review C, 2008
Measurements of the double-differential charged pion production cross-section in the range of momentum 100 MeV/c < p < 800 MeV/c and angle 0.35 < \theta < 2.15 rad in proton-beryllium, proton-carbon, proton-aluminium, proton-copper, proton-tin, proton-tantalum and proton-lead collisions are presented. The data were taken with the large acceptance HARP detector in the T9 beam line of the CERN PS. The pions were produced by proton beams in a momentum range from 3 GeV/c to 12.9 GeV/c hitting a target with a thickness of 5% of a nuclear interaction length.
Production in proton–proton collisions at
2012
The reaction pp→ppπ 0 π 0 has been investigated at a beam energy of 1.4 GeV using the WASA-at-COSY facility. The total cross section is found to be (324 ± 21 systematic ± 58 normalization ) µb. In order to study the production mechanism, differential kinematical distributions have been evaluated. The differential distributions indicate that both initial state protons are excited into intermediate ∆(1232) resonances, each decaying into a proton and a single pion, thereby producing the pion pair in the final state. No significant contribution of the Roper resonance N * (1440) via its decay into a proton and two pions is found.
Physical Review C, 2000
Pion excitation functions in proton-nucleus collisions, from the absolute threshold to 500 MeV, have been measured with 1 MeV beam energy resolution at the CELSIUS storage ring, operating in slow ramping mode. Total yields, angular distributions, and target mass dependence of ϩ production are generally reproduced well by QMD calculations. The ϩ / Ϫ ratios are not reproduced equally well, obviously because the detailed description of the pion interaction with the Coulomb field is very delicate.
\pi^0 \pi^0 Production in Proton-Proton Collisions at Tp=1.4 GeV
2011
The reaction pp->pppi0pi0 has been investigated at a beam energy of 1.4 GeV using the WASA-at-COSY facility. The total cross section is found to be (324 +- 21_systematic +- 58_normalization) mub. In order to to study the production mechanism, differential kinematical distributions have been evaluated. The differential distributions indicate that both initial state protons are excited into intermediate Delta(1232) resonances, each decaying into a proton and a single pion, thereby producing the pion pair in the final state. No significant contribution of the Roper resonance N*(1440) via its decay into a proton and two pions is found
The European Physical Journal C, 2007
A precision measurement of the double-differential production cross-section, d 2 σ π + /dpdΩ, for pions of positive charge, performed in the HARP experiment is presented. The incident particles are protons of 12.9 GeV/c momentum impinging on an aluminium target of 5% nuclear interaction length. The measurement of this cross-section has a direct application to the calculation of the neutrino flux of the K2K experiment. After cuts, 210 000 secondary tracks reconstructed in the forward spectrometer were used in this analysis. The results are given for secondaries within a momentum range from 0.75 GeV/c to 6.5 GeV/c, and within an angular range from 30 mrad to 210 mrad. The absolute normalization was performed using prescaled beam triggers counting protons on target. The overall scale of the cross-section is known to better than 6%, while the average point-to-point error is 8.2%.
Measurement of the production cross-section of positive pions in< i> p–Al collisions at 12.9 GeV/c
2006
A precision measurement of the double-differential production cross-section, d 2 σ π + /dpdΩ, for pions of positive charge, performed in the HARP experiment is presented. The incident particles are protons of 12.9 GeV/c momentum impinging on an aluminium target of 5% nuclear interaction length. The measurement of this cross-section has a direct application to the calculation of the neutrino flux of the K2K experiment. After cuts, 210 000 secondary tracks reconstructed in the forward spectrometer were used in this analysis. The results are given for secondaries within a momentum range from 0.75 GeV/c to 6.5 GeV/c, and within an angular range from 30 mrad to 210 mrad. The absolute normalization was performed using prescaled beam triggers counting protons on target. The overall scale of the cross-section is known to better than 6%, while the average point-to-point error is 8.2%.
Cross-Section Parameterizations for Pion and Nucleon Production From Negative Pion-Proton Collisions
Ranft has provided parameterizations of Lorentz invariant differential cross sections for pion and nucleon production in pion-proton collisions that are compared to some recent data. The Ranft parameterizations are then numerically integrated to form spectral and total cross sections. These numerical integrations are further parameterized to provide formulas for spectral and total cross sections suitable for use in radiation transport codes. The reactions that are analysed are for charged pions in the initial state and for both charged and neutral pions in the Þnal state.